This contains significant rebase / merge / testing work by Naut
<lbrynaut@protonmail.com>, Anthony Fieroni <bvbfan@abv.bg> and Brannon
King <countprimes@gmail.com>.
Documentation more readable when viewed on Github.
Some extra changes by @laanwj:
- Make README.usage the default README. This is more convenient from a
user perspective. Link to other documentation in this default README
- Add list of popular targets for cross compilation, change default to
Win64 instead of Win32